scholarly journals Variables Affecting NOx Formation in Lean-Premixed Combustion

1997 ◽  
Vol 119 (1) ◽  
pp. 102-107 ◽  
Author(s):  
R. C. Steele ◽  
A. C. Jarrett ◽  
P. C. Malte ◽  
J. H. Tonouchi ◽  
D. G. Nicol
Keyword(s):  
Residence Time ◽  
Combustion Temperature ◽  
Flow Reactor ◽  
Plug Flow ◽  
Volume Ratio ◽  
Chemical Reactor ◽  
Inlet Temperature ◽  
Reactor Model ◽  
Reactor Modeling ◽  
Lean Premixed

The formation of NOx in lean-premixed, high-intensity combustion is examined as a function of several of the relevant variables. The variables are the combustion temperature and pressure, fuel type, combustion zone residence time, mixture inlet temperature, reactor surface-to-volume ratio, and inlet jet size. The effects of these variables are examined by using jet-stirred reactors and chemical reactor modeling. The atmospheric pressure experiments have been completed and are fully reported. The results cover the combustion temperature range (measured) of 1500 to 1850 K, and include the following four fuels: methane, ethylene, propane, and carbon monoxide/hydrogen mixtures. The reactor residence time is varied from 1.7 to 7.4 ms, with most of the work done at 3.5 ms. The mixture inlet temperature is taken as 300 and 600 K, and two inlet jet sizes are used. Elevated pressure experiments are reported for pressures up to 7.1 atm for methane combustion at 4.0 ms with a mixture inlet temperature of 300 K. Experimental results are compared to chemical reactor modeling. This is accomplished by using a detailed chemical kinetic mechanism in a chemical reactor model, consisting of a perfectly stirred reactor (PSR) followed by a plug flow reactor (PFR). The methane results are also compared to several laboratory-scale and industrial-scale burners operated at simulated gas turbine engine conditions.

scholarly journals Variables Affecting NOx Formation in Lean-Premixed Combustion

1995 ◽  
Author(s):  
R. C. Steele ◽  
A. C. Jarrett ◽  
P. C. Malte ◽  
J. H. Tonouchi ◽  
D. G. Nicol
Keyword(s):  
Residence Time ◽  
Combustion Temperature ◽  
Flow Reactor ◽  
Plug Flow ◽  
Volume Ratio ◽  
Chemical Reactor ◽  
Inlet Temperature ◽  
Reactor Model ◽  
Reactor Modeling ◽  
Lean Premixed

The formation of NOx in lean-premixed, high-intensity combustion is examined as a function of several of the relevant variables. The variables are the combustion temperature and pressure, fuel-type, combustion zone residence time, mixture inlet temperature, reactor surface-to-volume ratio, and inlet jet size. The effects of these variables are examined by using jet-stirred reactors and chemical reactor modeling. The atmospheric pressure experiments have been completed and are fully reported. The results cover the combustion temperature range (measured) of 1500 to 1850K, and include the following four fuels: methane, ethylene, propane, and carbon monoxide/hydrogen mixtures. The reactor residence time is varied from 1.7 to 7.4ms, with most of the work done at 3.5ms. The mixture inlet temperature is taken as 300 and 600K, and two inlet jet sizes are used. Elevated pressure experiments are reported for pressures up to 7.1atm for methane combustion at 4.0ms with a mixture inlet temperature of 300K. Experimental results are compared to chemical reactor modeling. This is accomplished by using a detailed chemical kinetic mechanism in a chemical reactor model, consisting of a perfectly stirred reactor (PSR) followed by a plug flow reactor (PFR). The methane results are also compared to several laboratory-scale and industrial-scale burners operated at simulated gas turbine engine conditions.

Simplified Models for NOx Production Rates in Lean-Premixed Combustion

1994 ◽  
Author(s):  
David G. Nicol ◽  
Philip C. Malte ◽  
Robert C. Steele
Keyword(s):  
Laboratory Data ◽  
Chemical Reactor ◽  
Premixed Combustion ◽  
Empirical Correlations ◽  
Simplified Models ◽  
Reactor Modeling ◽  
Lean Premixed Combustion ◽  
Co Concentration ◽  
Lean Premixed ◽  
Recent Laboratory

Simplified models for predicting the rate of production of NOx in lean-premixed combustion are presented. These models are based on chemical reactor modeling, and are influenced strongly by the nitrous oxide mechanism, which is an important source of NOx in lean-premixed combustion. They include 1) the minimum set of reactions required for predicting the NOx production, and 2) empirical correlations of the NOx production rate as a function of the CO concentration. The later have been developed for use in an NOx post-processor for CFD codes. Also presented are recent laboratory data, which support the chemical rates used in this study.

Chemical Kinetic Analysis of a Flameless Gas Turbine Combustor

2008 ◽  
Author(s):  
G. Arvind Rao ◽  
Yeshayahou Levy ◽  
Ephraim J. Gutmark
Keyword(s):  
Combustion Chamber ◽  
Kinetic Analysis ◽  
Gas Turbine ◽  
Flame Temperature ◽  
Plug Flow ◽  
Combustion Process ◽  
Chemical Reactor ◽  
Chemical Kinetic ◽  
Combustion Regime ◽  
Reactor Model

Flameless combustion (FC) is one of the most promising techniques of reducing harmful emissions from combustion systems. FC is a combustion phenomenon that takes place at low O2 concentration and high inlet reactant temperature. This unique combination results in a distributed combustion regime with a lower adiabatic flame temperature. The paper focuses on investigating the chemical kinetics of an prototype combustion chamber built at the university of Cincinnati with an aim of establishing flameless regime and demonstrating the applicability of FC to gas turbine engines. A Chemical reactor model (CRM) has been built for emulating the reactions within the combustor. The entire combustion chamber has been divided into appropriate number of Perfectly Stirred Reactors (PSRs) and Plug Flow Reactors (PFRs). The interconnections between these reactors and the residence times of these reactors are based on the PIV studies of the combustor flow field. The CRM model has then been used to predict the combustor emission profile for various equivalence ratios. The results obtained from CRM model show that the emission from the combustor are quite less at low equivalence ratios and have been found to be in reasonable agreement with experimental observations. The chemical kinetic analysis gives an insight on the role of vitiated combustion gases in suppressing the formation of pollutants within the combustion process.

Optimisation of CO Turndown for an Axially Staged Gas Turbine Combustor

2020 ◽  
Author(s):  
Jacob E. Rivera ◽  
Robert L. Gordon ◽  
Mohsen Talei ◽  
Gilles Bourque
Keyword(s):  
Residence Time ◽  
Parametric Study ◽  
Gas Turbines ◽  
Flow Reactor ◽  
Operating Conditions ◽  
Independent Effect ◽  
Inlet Temperature ◽  
Operating Characteristics ◽  
Two Stage ◽  
The Impact

Abstract This paper reports on an optimisation study of the CO turndown behaviour of an axially staged combustor, in the context of industrial gas turbines (GT). The aim of this work is to assess the optimally achievable CO turndown behaviour limit given system and operating characteristics, without considering flow-induced behaviours such as mixing quality and flame spatial characteristics. To that end, chemical reactor network modelling is used to investigate the impact of various system and operating conditions on the exhaust CO emissions of each combustion stage, as well as at the combustor exit. Different combustor residence time combinations are explored to determine their contribution to the exhaust CO emissions. The two-stage combustor modelled in this study consists of a primary (Py) and a secondary (Sy) combustion stage, followed by a discharge nozzle (DN), which distributes the exhaust to the turbines. The Py is modelled using a freely propagating flame (FPF), with the exhaust gas extracted downstream of the flame front at a specific location corresponding to a specified residence time (tr). These exhaust gases are then mixed and combusted with fresh gases in the Sy, modelled by a perfectly stirred reactor (PSR) operating within a set tr. These combined gases then flow into the DN, which is modelled by a plug flow reactor (PFR) that cools the gas to varying combustor exit temperatures within a constrained tr. Together, these form a simplified CRN model of a two-stage, dry-low emissions (DLE) combustion system. Using this CRN model, the impact of the tr distribution between the Py, Sy and DN is explored. A parametric study is conducted to determine how inlet pressure (Pin), inlet temperature (Tin), equivalence ratio (ϕ) and Py-Sy fuel split (FS), individually impact indicative CO turndown behaviour. Their coupling throughout engine load is then investigated using a model combustor, and its effect on CO turndown is explored. Thus, this aims to deduce the fundamental, chemically-driven parameters considered to be most important for identifying the optimal CO turndown of GT combustors. In this work, a parametric study and a model combustor study are presented. The parametric study consists of changing a single parameter at a time, to observe the independent effect of this change and determine its contribution to CO turndown behaviour. The model combustor study uses the same CRN, and varies the parameters simultaneously to mimic their change as an engine moves through its steady-state power curve. The latter study thus elucidates the difference in CO turndown behaviour when all operating conditions are coupled, as they are in practical engines. The results of this study aim to demonstrate the parameters that are key for optimising and improving CO turndown.

scholarly journals Explicit Residence Time Distribution of a Generalised Cascade of Continuous Stirred Tank Reactors for a Description of Short Recirculation Time (Bypassing)

Processes ◽  
2019 ◽  
Vol 7 (9) ◽  
pp. 615 ◽  
Author(s):  
Peter Toson ◽  
Pankaj Doshi ◽  
Dalibor Jajcevic
Keyword(s):  
Residence Time ◽  
Time Distribution ◽  
Residence Time Distribution ◽  
Flow Reactor ◽  
Plug Flow ◽  
Stirred Tank ◽  
Stirred Tank Reactors ◽  
Delayed Impulse ◽  
In Series ◽  
Back Mixing

The tanks-in-series model (TIS) is a popular model to describe the residence time distribution (RTD) of non-ideal continuously stirred tank reactors (CSTRs) with limited back-mixing. In this work, the TIS model was generalised to a cascade of n CSTRs with non-integer non-negative n. The resulting model describes non-ideal back-mixing with n > 1. However, the most interesting feature of the n-CSTR model is the ability to describe short recirculation times (bypassing) with n < 1 without the need of complex reactor networks. The n-CSTR model is the only model that connects the three fundamental RTDs occurring in reactor modelling by variation of a single shape parameter n: The unit impulse at n→0, the exponential RTD of an ideal CSTR at n = 1, and the delayed impulse of an ideal plug flow reactor at n→∞. The n-CSTR model can be used as a stand-alone model or as part of a reactor network. The bypassing material fraction for the regime n < 1 was analysed. Finally, a Fourier analysis of the n-CSTR was performed to predict the ability of a unit operation to filter out upstream fluctuations and to model the response to upstream set point changes.

scholarly journals Reversible Molten Catalytic Methane Cracking Applied to Commercial Solar-Thermal Receivers

Energies ◽  
2020 ◽  
Vol 13 (23) ◽  
pp. 6229
Author(s):  
Scott C. Rowe ◽  
Taylor A. Ariko ◽  
Kaylin M. Weiler ◽  
Jacob T. E. Spana ◽  
Alan W. Weimer
Keyword(s):  
Flow Reactor ◽  
Plug Flow ◽  
Hydrogen Fuel ◽  
Reactor Model ◽  
Solar Reactor ◽  
Greenhouse Emissions ◽  
Solar Reactors ◽  
And Performance ◽  
Methane Cracking ◽  
Technology Demonstrator

When driven by sunlight, molten catalytic methane cracking can produce clean hydrogen fuel from natural gas without greenhouse emissions. To design solar methane crackers, a canonical plug flow reactor model was developed that spanned industrially relevant temperatures and pressures (1150–1350 Kelvin and 2–200 atmospheres). This model was then validated against published methane cracking data and used to screen power tower and beam-down reactor designs based on “Solar Two,” a renewables technology demonstrator from the 1990s. Overall, catalytic molten methane cracking is likely feasible in commercial beam-down solar reactors, but not power towers. The best beam-down reactor design was 9% efficient in the capture of sunlight as fungible hydrogen fuel, which approaches photovoltaic efficiencies. Conversely, the best discovered tower methane cracker was only 1.7% efficient. Thus, a beam-down reactor is likely tractable for solar methane cracking, whereas power tower configurations appear infeasible. However, the best simulated commercial reactors were heat transfer limited, not reaction limited. Efficiencies could be higher if heat bottlenecks are removed from solar methane cracker designs. This work sets benchmark conditions and performance for future solar reactor improvement via design innovation and multiphysics simulation.

scholarly journals Effects of Incomplete Premixing on NOx Formation at Temperature and Pressure Conditions of LP Combustion Turbines

1997 ◽  
Author(s):  
Teodora Rutar ◽  
Scott M. Martin ◽  
David G. Nicol ◽  
Philip C. Malte ◽  
David T. Pratt
Keyword(s):  
Air Temperature ◽  
Chemical Reactor ◽  
Nox Emissions ◽  
Reactor Model ◽  
Nox Formation ◽  
Air Temperatures ◽  
Primary Zone ◽  
Lean Premixed ◽  
Temperature And Pressure

A probability density function/chemical reactor model (PDF/CRM) is applied to study how NOx emissions vary with mean combustion temperature, inlet air temperature, and pressure for different degrees of premixing quality under lean-premixed (LP) gas turbine combustor conditions. Inlet air temperatures of 550, 650 and 750 K, and combustor pressures of 10, 14 and 30 atm are examined in different chemical reactor configurations. Primary results from this study are: incomplete premixing can either increase or decrease NOx emissions, depending on the primary zone stoichiometry; an Arrhenius-type plot of NOx emissions may have promise for assessing the premixer quality of lean-premixed combustors; and decreasing premixing quality enhances the influence of inlet air temperature and pressure on NOx emissions.

Sign in / Sign up

Export Citation Format

Share Document